import asyncio
import json
import os
import difflib
import fnmatch
import shutil
from typing import Optional, Dict, Any, Tuple

from src.constants import MAX_READ_CHARS, MAX_DIFF_LINES, MAX_OUTPUT_CHARS

_CODENAV_SKIP_DIRS = frozenset({
    ".git", ".hg", ".svn", "node_modules", "venv", ".venv", "__pycache__",
    ".mypy_cache", ".pytest_cache", ".ruff_cache", "dist", "build",
    ".next", ".cache", "site-packages", ".idea", ".tox",
})
_CODENAV_MAX_HITS = 200
_CODENAV_MAX_LINE = 400

def _unified_diff(old: str, new: str, path: str) -> Optional[Dict[str, Any]]:
    if old == new:
        return None
    old_lines = old.splitlines()
    new_lines = new.splitlines()
    label = path or "file"
    diff_lines = list(difflib.unified_diff(
        old_lines, new_lines,
        fromfile=f"a/{label}", tofile=f"b/{label}",
        lineterm="",
    ))
    added = sum(1 for line in diff_lines if line.startswith("+") and not line.startswith("+++"))
    removed = sum(1 for line in diff_lines if line.startswith("-") and not line.startswith("---"))
    truncated = False
    if len(diff_lines) > MAX_DIFF_LINES:
        diff_lines = diff_lines[:MAX_DIFF_LINES]
        truncated = True
    text = "\n".join(diff_lines)
    if truncated:
        text += f"\n… diff truncated at {MAX_DIFF_LINES} lines"
    return {
        "text": text,
        "added": added,
        "removed": removed,
        "new_file": old == "",
        "file": os.path.basename(path) or (path or "file"),
    }

class EditFileTool:
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import _resolve_tool_path, _resolve_search_root, _truncate
        try:
            args = json.loads(content) if content.strip().startswith("{") else {}
        except (json.JSONDecodeError, TypeError):
            args = {}
        raw_path = (args.get("path") or "").strip()
        old = args.get("old_string", "")
        new = args.get("new_string", "")
        replace_all = bool(args.get("replace_all", False))
        if not raw_path:
            return {"error": "edit_file: path required", "exit_code": 1}
        try:
            path = _resolve_tool_path(raw_path)
        except ValueError as e:
            return {"error": f"edit_file: {e}", "exit_code": 1}
        if old == "":
            return {"error": "edit_file: old_string required (use write_file to create a file)", "exit_code": 1}
        if old == new:
            return {"error": "edit_file: old_string and new_string are identical", "exit_code": 1}

        def _apply():
            """Helper function that performs the actual string replacement and file writing logic."""
            with open(path, "r", encoding="utf-8") as f:
                original = f.read()
            count = original.count(old)
            if count == 0:
                return original, None, "not_found"
            if count > 1 and not replace_all:
                return original, None, f"not_unique:{count}"
            updated = original.replace(old, new) if replace_all else original.replace(old, new, 1)
            with open(path, "w", encoding="utf-8") as f:
                f.write(updated)
            return original, updated, "ok"

        try:
            original, updated, status = await asyncio.to_thread(_apply)
        except FileNotFoundError:
            return {"error": f"edit_file: {path}: not found (use write_file to create it)", "exit_code": 1}
        except (IsADirectoryError, UnicodeDecodeError):
            return {"error": f"edit_file: {path}: not an editable text file", "exit_code": 1}
        except PermissionError:
            return {"error": f"edit_file: {path}: permission denied", "exit_code": 1}
        except OSError as e:
            return {"error": f"edit_file: {path}: {e}", "exit_code": 1}

        if status == "not_found":
            return {"error": f"edit_file: old_string not found in {path}. Read the file and match it exactly.", "exit_code": 1}
        if status.startswith("not_unique"):
            n = status.split(":", 1)[1]
            return {"error": f"edit_file: old_string is not unique in {path} ({n} matches). Add surrounding context or set replace_all=true.", "exit_code": 1}

        n = original.count(old)
        result = {"output": f"Edited {path} ({n} replacement{'s' if n != 1 else ''})", "exit_code": 0}
        diff = _unified_diff(original, updated, path)
        if diff:
            result["diff"] = diff
        return result

class ReadFileTool:
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import _resolve_tool_path, _resolve_search_root, _truncate
        raw_path, offset, limit = content.split("\n", 1)[0].strip(), 0, 0
        _stripped = content.strip()
        if _stripped.startswith("{"):
            try:
                _a = json.loads(_stripped)
                raw_path = str(_a.get("path", "")).strip()
                offset = int(_a.get("offset") or 0)
                limit = int(_a.get("limit") or 0)
            except (json.JSONDecodeError, TypeError, ValueError):
                pass
        try:
            path = _resolve_tool_path(raw_path)
        except ValueError as e:
            return {"error": f"read_file: {e}", "exit_code": 1}
        try:
            def _read():
                if offset > 0 or limit > 0:
                    start = max(offset, 1)
                    out, n, budget = [], 0, MAX_READ_CHARS
                    with open(path, "r", encoding="utf-8", errors="replace") as f:
                        for i, line in enumerate(f, 1):
                            if i < start:
                                continue
                            if limit > 0 and n >= limit:
                                break
                            out.append(line)
                            n += 1
                            budget -= len(line)
                            if budget <= 0:
                                out.append(f"\n... [truncated at {MAX_READ_CHARS} chars]")
                                break
                    return "".join(out)
                with open(path, "r", encoding="utf-8", errors="replace") as f:
                    return f.read(MAX_READ_CHARS + 1)
            data = await asyncio.to_thread(_read)
        except FileNotFoundError:
            return {"error": f"read_file: {path}: not found", "exit_code": 1}
        except PermissionError:
            return {"error": f"read_file: {path}: permission denied", "exit_code": 1}
        except IsADirectoryError:
            return {"error": f"read_file: {path}: is a directory (use ls)", "exit_code": 1}
        except OSError as e:
            return {"error": f"read_file: {path}: {e}", "exit_code": 1}
        if not (offset > 0 or limit > 0) and len(data) > MAX_READ_CHARS:
            data = data[:MAX_READ_CHARS] + f"\n... [truncated at {MAX_READ_CHARS} chars]"
        return {"output": data, "exit_code": 0}

class WriteFileTool:
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import _resolve_tool_path, _resolve_search_root, _truncate
        lines = content.split("\n", 1)
        raw_path = lines[0].strip()
        body = lines[1] if len(lines) > 1 else ""
        try:
            path = _resolve_tool_path(raw_path)
        except ValueError as e:
            return {"error": f"write_file: {e}", "exit_code": 1}
        try:
            def _write():
                old = ""
                try:
                    with open(path, "r", encoding="utf-8") as f:
                        old = f.read()
                except (FileNotFoundError, IsADirectoryError, UnicodeDecodeError, OSError):
                    old = ""
                d = os.path.dirname(path)
                if d:
                    os.makedirs(d, exist_ok=True)
                with open(path, "w", encoding="utf-8") as f:
                    f.write(body)
                return old, len(body)
            old_content, size = await asyncio.to_thread(_write)
        except PermissionError:
            return {"error": f"write_file: {path}: permission denied", "exit_code": 1}
        except OSError as e:
            return {"error": f"write_file: {path}: {e}", "exit_code": 1}
        diff = _unified_diff(old_content, body, path)
        result = {"output": f"Wrote {size} bytes to {path}", "exit_code": 0}
        if diff:
            result["diff"] = diff
        return result

class LsTool:
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import _resolve_tool_path, _resolve_search_root, _truncate
        raw_path = ""
        _s = (content or "").strip()
        if _s.startswith("{"):
            try:
                raw_path = str(json.loads(_s).get("path", "")).strip()
            except json.JSONDecodeError:
                raw_path = ""
        else:
            raw_path = _s.split("\n", 1)[0].strip()
        try:
            root = _resolve_search_root(raw_path)
        except ValueError as e:
            return {"error": f"ls: {e}", "exit_code": 1}

        def _ls():
            if not os.path.isdir(root):
                return None, f"ls: {root}: not a directory"
            rows = []
            try:
                with os.scandir(root) as it:
                    for entry in it:
                        if entry.name.startswith("."):
                            continue
                        try:
                            is_dir = entry.is_dir(follow_symlinks=False)
                            size = entry.stat(follow_symlinks=False).st_size if not is_dir else 0
                        except OSError:
                            continue
                        rows.append((is_dir, entry.name, size))
            except (PermissionError, OSError) as _e:
                return None, f"ls: {_e}"
            rows.sort(key=lambda r: (not r[0], r[1].lower()))
            lines = [f"{root}:"]
            for is_dir, name, size in rows[:_CODENAV_MAX_HITS]:
                lines.append(f"  {name}/" if is_dir else f"  {name}  ({size} B)")
            if len(rows) > _CODENAV_MAX_HITS:
                lines.append(f"  ... [{len(rows) - _CODENAV_MAX_HITS} more]")
            if not rows:
                lines.append("  (empty)")
            return "\n".join(lines), None

        out, err = await asyncio.to_thread(_ls)
        if err:
            return {"error": err, "exit_code": 1}
        return {"output": _truncate(out), "exit_code": 0}

class GlobTool:
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import _resolve_tool_path, _resolve_search_root, _truncate
        args = {}
        _s = (content or "").strip()
        if _s.startswith("{"):
            try:
                args = json.loads(_s)
            except json.JSONDecodeError:
                args = {}
        else:
            args = {"pattern": _s}
        pattern = str(args.get("pattern", "")).strip()
        if not pattern:
            return {"error": "glob: pattern is required", "exit_code": 1}
        try:
            root = _resolve_search_root(str(args.get("path", "")))
        except ValueError as e:
            return {"error": f"glob: {e}", "exit_code": 1}

        def _glob():
            from pathlib import Path
            base = Path(root)
            if not base.is_dir():
                return None, f"glob: {root}: not a directory"
            matched = []
            try:
                for p in base.rglob(pattern):
                    if set(p.relative_to(base).parts) & _CODENAV_SKIP_DIRS:
                        continue
                    try:
                        mtime = p.stat().st_mtime
                    except OSError:
                        mtime = 0
                    matched.append((mtime, str(p)))
                    if len(matched) > _CODENAV_MAX_HITS * 5:
                        break
            except (OSError, ValueError) as _e:
                return None, f"glob: {_e}"
            matched.sort(key=lambda t: t[0], reverse=True)
            return [pth for _, pth in matched[:_CODENAV_MAX_HITS]], None

        paths, err = await asyncio.to_thread(_glob)
        if err:
            return {"error": err, "exit_code": 1}
        if not paths:
            return {"output": f"No files matching {pattern!r} under {root}", "exit_code": 0}
        out = "\n".join(paths)
        if len(paths) >= _CODENAV_MAX_HITS:
            out += f"\n... [capped at {_CODENAV_MAX_HITS} files]"
        return {"output": _truncate(out), "exit_code": 0}

class GrepTool:
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import _resolve_tool_path, _resolve_search_root, _truncate
        args: Dict[str, Any] = {}
        _s = (content or "").strip()
        if _s.startswith("{"):
            try:
                args = json.loads(_s)
            except json.JSONDecodeError:
                args = {}
        else:
            args = {"pattern": _s}
        pattern = str(args.get("pattern", "")).strip()
        if not pattern:
            return {"error": "grep: pattern is required", "exit_code": 1}
        ignore_case = bool(args.get("ignore_case"))
        glob_pat = str(args.get("glob", "") or "").strip()
        try:
            max_hits = int(args.get("max_results") or _CODENAV_MAX_HITS)
        except (TypeError, ValueError):
            max_hits = _CODENAV_MAX_HITS
        max_hits = max(1, min(max_hits, _CODENAV_MAX_HITS))
        try:
            root = _resolve_search_root(str(args.get("path", "")))
        except ValueError as e:
            return {"error": f"grep: {e}", "exit_code": 1}

        def _grep():
            import re as _re
            import shutil
            rg = shutil.which("rg")
            if rg:
                cmd = [rg, "--line-number", "--no-heading", "--color=never",
                       "--max-count", str(max_hits)]
                if ignore_case:
                    cmd.append("--ignore-case")
                if glob_pat:
                    cmd += ["--glob", glob_pat]
                for _d in _CODENAV_SKIP_DIRS:
                    cmd += ["--glob", f"!**/{_d}/**"]
                cmd += ["--regexp", pattern, root]
                try:
                    import subprocess
                    p = subprocess.run(cmd, capture_output=True, text=True, timeout=20)
                    lines = [ln for ln in (p.stdout or "").splitlines() if ln][:max_hits]
                    return lines, None
                except subprocess.TimeoutExpired:
                    return None, "grep: timed out"
                except Exception as _e:
                    return None, f"grep: {_e}"
            try:
                rx = _re.compile(pattern, _re.IGNORECASE if ignore_case else 0)
            except _re.error as _e:
                return None, f"grep: bad pattern: {_e}"
            hits = []
            if os.path.isfile(root):
                file_iter = [root]
            else:
                file_iter = []
                for dp, dns, fns in os.walk(root):
                    dns[:] = [d for d in dns if d not in _CODENAV_SKIP_DIRS]
                    for fn in fns:
                        if glob_pat and not fnmatch.fnmatch(fn, glob_pat):
                            continue
                        file_iter.append(os.path.join(dp, fn))
            for fp in file_iter:
                if len(hits) >= max_hits:
                    break
                try:
                    with open(fp, "r", encoding="utf-8", errors="strict") as f:
                        for i, line in enumerate(f, 1):
                            if rx.search(line):
                                hits.append(f"{fp}:{i}:{line.rstrip()[:_CODENAV_MAX_LINE]}")
                                if len(hits) >= max_hits:
                                    break
                except (UnicodeDecodeError, OSError):
                    continue
            return hits, None

        lines, err = await asyncio.to_thread(_grep)
        if err:
            return {"error": err, "exit_code": 1}
        if not lines:
            return {"output": f"No matches for {pattern!r} under {root}", "exit_code": 0}
        out = "\n".join(ln[:_CODENAV_MAX_LINE] for ln in lines)
        if len(lines) >= max_hits:
            out += f"\n... [capped at {max_hits} matches]"
        return {"output": _truncate(out), "exit_code": 0}

class GetWorkspaceTool:
    """Report the active workspace folder (no args). File tools are confined to
    it; the shell starts there (cwd) but is NOT sandboxed."""
    async def execute(self, content: str, ctx: dict) -> dict:
        from src.tool_execution import get_active_workspace
        ws = get_active_workspace()
        if ws:
            return {
                "output": f"{ws}\n(File tools are confined to this folder; the shell starts "
                          f"here but is not sandboxed and can reach outside it.)",
                "exit_code": 0,
            }
        return {
            "output": "No workspace is set. File tools use the default allowed roots; "
                      "resolve paths from the user or use absolute paths.",
            "exit_code": 0,
        }